Driving method and device of electro-optic element, and electronic equipment

a technology of electrooptic elements and driving methods, applied in the direction of color television details, television systems, instruments, etc., can solve the problems of power consumption, different levels of grayscale of pixels, and increased number of times a voltage is written into pixels during one frame period

Inactive Publication Date: 2002-09-12
SEIKO EPSON CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009] In order to solve the above problems, the present invention has an object to provide pixel driving method and device as well as electronic equipment each capable of avoiding or preventing a difference in a level of grayscale from occurring resulting from the positions of the sub-fields selected irregularly.

Problems solved by technology

Hence, there is a problem that, for example, pixels display different levels of grayscale when they should display the same level of grayscale due to irregularity of the relation in terms of position among the selected sub-fields.
Also, in the case of the driving with (2.sup.N-1) sub-fields in the conventional 2.sup.N-level grayscale, there are so many sub-fields that the number of times a voltage is written into the pixels during one frame period is increased, and so is the power consumption.
Further, because it is necessary to increase the number of levels of grayscale, that is, to further shorten the length of each sub-field with an increasing number of levels of grayscale, the data signal has to be applied under time constraints, which poses a problem that it is difficult to control the application of the data signal with a high accuracy.

Method used

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  • Driving method and device of electro-optic element, and electronic equipment
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  • Driving method and device of electro-optic element, and electronic equipment

Examples

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first embodiment

[0054] (First embodiment)

[0055] The following description will describe an electro-optic device using a sub-field driving method, which is the pixel driving method according to the present invention.

[0056] FIG. 1 shows an arrangement of an electro-optic device of a first embodiment. The electro-optic device is provided with a plurality of pixels aligned in a matrix between an element substrate and a counter substrate, and a predetermined number of pixels aligned in the row direction (X) are selected concurrently and such a selection is performed sequentially in a vertical direction, that is, line-sequentially, while a signal defining a level of grayscale, that is, 0 or .+-.V, is applied to the pixels within one frame, that is, during a period of one frame, thereby allowing each pixel to display that level of grayscale. To be more specific, the electro-optic device selects, for example, a predetermined number of pixels aligned in one row in each of a plurality of sub-fields that toge...

second embodiment

[0124] (Second embodiment)

[0125] The following description will describe an electro-optic device of a second embodiment with reference to FIGS. 16 through 19.

[0126] FIG. 19 shows sub-fields in the second embodiment. As is apparent from the comparison of FIG. 19 with FIG. 10 showing the sub-fields in the first embodiment, a sub-field SF8 that is always kept switched OFF regardless of the grayscale data is additionally provided in a frame 1F in the second embodiment.

[0127] FIG. 16 shows an arrangement of a start pulse generating circuit of the second embodiment. FIG. 17 shows an arrangement of a data converting circuit of the second embodiment. FIG. 18 shows waveforms of signals in the second embodiment. The electro-optic device of the second embodiment includes the start pulse generating circuit 210 shown in FIG. 16 and the data converting circuit 300 shown in FIG. 12 so as to operate by using the sub-field SF8. In the start pulse generating circuit 210, as shown in FIG. 16, a multip...

third embodiment

[0129] (Third embodiment)

[0130] An electro-optic device of a third embodiment is characterized by displaying a greater number of levels of grayscale than the electro-optic devices of the first and second embodiments. The following description will describe the electro-optic device of the third embodiment with reference to FIGS. 15 through 18.

[0131] FIG. 23 shows sub-fields in the third embodiment. According to the electro-optic device of the third embodiment, in order to display 64-level grayscale defined by 6-bit grayscale data D0-D5 inputted into the electro-optic device, one frame (1F) includes, as shown in FIG. 23, seven sub-fields SF1-SF7, seven sub-fields SF9-SF15, and a sub-field SF8. The length of the sub-fields SF1-SF7 has a weight for the level 1, and the length of the sub-fields SF9-SF15 has a weight for the level 8. In order to give a threshold voltage Vth that is defined by the performance characteristics of the liquid crystals, the sub-field SF8 is always kept switched...

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PUM

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Abstract

With the conventional technique, pixels displays different levels of grayscale resulting from irregularity of a relation in terms of position among selected sub-fields, when the same level of grayscale should be displayed. A pixel driving method according to the present invention includes: a selecting step of sequentially selecting, according to grayscale data, a plurality of first sub-field periods continuous with respect to one another and a plurality of second sub-field periods continuous with respect to one another and following consecutively the plurality of first sub-field periods in a direction moving away from a boundary of the plurality of first sub-field periods and the plurality of second sub-field periods, which is given as the origin; and a driving step of switching ON pixels during the selected sub-field periods.

Description

BACKGROUND OF THE INVENTION[0001] 1. Field of Invention[0002] The present invention relates to pixel driving method and device for driving pixels, which are electro-optic elements, by means of pulse width modulation, and to electronic equipment.[0003] 2. Description of Related Art[0004] Conventionally, a pixel driving method for driving a plurality of pixels aligned in a matrix-wise manner by using a scanning signal for selecting the pixels and a data signal for defining the level of grayscale the pixels should display is used. As the pixel driving method, sub-field driving that applies the data signal to all the pixels in each of a plurality of periods (hereinafter, referred to as sub-fields) provided within one frame has been proposed to improve an image quality of a display image.[0005] According to the sub-field driving, either of two voltages, a voltage (for example, high pulse) that displays ON (for example, black) and a voltage (low pulse) that displays OFF (for example, whit...

Claims

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Application Information

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IPC IPC(8): G02F1/133G02F1/13G09G3/20G09G3/36H04N5/66
CPCG09G3/20G09G3/2025G09G3/2029G09G3/2033G09G3/2077G09G3/3648G09G2300/0809G09G2310/0275G02F1/13
InventorKOJIMA, DAISUKEITO, AKIHIKO
OwnerSEIKO EPSON CORP